It's fairly easy, actually. The only thing you need is Photoshop and about 20-9001 minutes (depending if you're good or not).
Firstly, I used the "clone stamp tool" to remove Skeletron and the text.
Secondly, I cut the billboard out, just to keep it for later, so I could place it over the re-added picture, just with a lower opasity so it would get the old bilboard paper effect from the original picture.
And thirdly, I placed a random picture which I had in my "pictures" folder, and I then proceeded to make it 3d and wrap it around the edges of the billboard. This is when the "billboard paper effect" comes it. I basically just placed it over the picture which I had added, and then it ended up looking like this.